Zincke et al, Ann. 343 86 (1905) used acetic acid to prepare alkylidene bis(dibromophenol) and recovered a product having a melting point of 162.degree.-163.degree. C. In British patent No. 614,235, the melting point is given as about 160.degree.-161.degree. C.
British patent No. 1,031,500 indicates that with glacial acetic acid after a reaction time of 1 to 2 days, the desired bromine derivative is separated from the mother liquor with a yield of 70-78 percent as an impure raw material which must be purified by recrystallizing.
German patent No. 1,129,957 describes bromination of bisphenol-A in 70-100 percent acetic acid using a mixture of bromine and chlorine as the brominating agent. German patent No. 1,151,811 also teaches use of the same solvent and brominating agent.
U.S. Pat. No. 3,234,289 teaches use of a post-heating step when tetrabromobisphenols are made by bromination in an alkanol-water solvent.
Using the process of this invention, I have prepared 4,4'-isopropylidene bis(2,6-dibromophenol) with a melting point as high as 180.degree.-182.degree. C.